壳聚糖在医药中的应用

壳聚糖（chitosan）是一种天然高分子化合物，是自然界第二大纤维来源。其化学名称为（1，4）-2-氨基-2-脱氧-β-D-葡萄糖，分子结构与纤维素相类似，分子呈直链状，极性强，易结晶。壳聚糖无毒，无害，具有良好的保湿性，能防止静电，化学稳定性良好，近年来，已在化工、食品、化妆品、环保、医药卫生等方面得到广泛的应用。     

N-乙酰化制备水溶性壳聚糖研究

以高脱乙酰度壳聚糖为原料,在不使用吡啶的无水乙醇均相体系中用乙酸酐通过N-乙酰化制备了水溶性壳聚糖,采用酸碱滴定、XRD、IR对壳聚糖原料和所制得水溶性壳聚糖的脱乙酰度、结晶状态、红外光谱分别进行了测试分析,并探讨了水溶性壳聚糖的结构与水溶性机理。     

Mn(Ⅱ)对壳聚糖降解制备低聚壳聚糖的影响

将壳聚糖进行液态均相配合反应制得壳聚糖锰配合物，IR、元素分析及热分析等检测证实了壳聚糖锰配合物中配位键的存在，且显示壳聚糖锰配合物存在有利于壳聚糖高分子链断裂的弱势结构。以H2O2对壳聚糖．Mn(Ⅱ)配合物及壳聚糖进行氧化降解，考察降解过程中粘度的变化及降解产物分子量分布，在相同的降解条件下，壳聚糖锰配合物的降解速度明显高于壳聚糖，且降解产物分子量分布较壳聚糖直接降解窄。对壳聚糖锰配合物降解反应动力学研究表明壳聚糖锰配合物对H2O2分解不存在催化作用，其降解反应与壳聚糖的差异只与其结构有关。对降解产物进行脱金属处理，所得低聚壳聚糖含锰量为0。     

纳米纤维素晶须-壳聚糖/聚乙烯醇复合膜性能与细胞相容性

以椰壳纤维为原料,制备了纳米纤维素晶须,用硅烷偶联剂对纳米纤维素晶须进行改性,将改性后纳米纤维素晶须与壳聚糖、聚乙烯醇共混,采用溶液浇铸法制备了改性纳米纤维素晶须-壳聚糖/聚乙烯醇复合膜。采用FTIR、DSC、TG、XRD和SEM对改性纳米纤维素晶须-壳聚糖/聚乙烯醇复合膜的结构、热性能、结晶行为和形貌进行表征与分析,对复合膜的力学性能和水接触角进行测试,将成纤维细胞L929接种到复合膜上,对其进行细胞相容性实验。结果表明,添加改性纤维素晶须,能够使壳聚糖/聚乙烯醇复合膜的热性能、结晶行为和力学性能提高,成纤维细胞在复合膜上具有较好的黏附和生长,制备的纳米纤维素晶须-壳聚糖/聚乙烯醇复合膜具有良好的综合性能和细胞相容性。     

壳聚糖辐射降解产物的水溶性研究

文中研究了壳聚糖γ辐射降解产物的水溶性规律。用凝胶渗透色谱(GPC)、傅立叶变换红外光谱(FT-IR)和X射线衍射(XRD)对降解产物进行表征分析。讨论了温度、辐射剂量、产物数均相对分子质量、产物化学结构以及结晶形态对溶解度的影响。结果表明,随着辐射剂量增加,数均相对分子质量的不断减小,产物在水中的溶解度不断增大。水溶性产物与不溶性产物在化学结构与结晶形态上存在明显差异。降解过程中壳聚糖结晶形态由初始的α态向β态转变,结晶度不断下降。一定条件下,结晶形态是决定产物水溶性的主要因素。     

羧甲基壳聚糖合成条件的优化及产物结构表征

通过异相法的方法合成了絮凝剂羧甲基壳聚糖．根据羧甲基壳聚糖对废水中Cd^2 的去除率，利用四因素三水平正交实验优化了羧甲基壳聚糖的合成条件。正交实验的结果表明优化反应条件为：反应时间7h，反应温度为50℃，氯乙酸对壳聚糖的质量比为1．25，氢氧化钠对壳聚糖的质量比为1．0。在此优化条件下得到的羧甲基壳聚糖产品对Cd^2 的最大去除率可达99．7％，用IR和^1H NMR对相应的产品进行了结构表征，结果表明羧甲基化反应发生在C2位上NH2处的程度高于C6位的OH。     

壳聚糖膜分离乙醇／水溶液的渗透汽化性能研究

以脱乙酰化度为77．5％的壳聚糖为原料，采用高温浓碱处理的方法得到脱酰化度为98．2％的壳聚糖，分别用这两种壳聚糖制膜，用于乙醇／水混合物的分离，结果表明在同样条件下，脱乙酰化度高的壳聚糖膜的分离性能优于脱乙酰化度低的壳聚糖膜。     

温和条件下壳聚糖酸催化降解制备氨基葡萄糖盐酸盐研究

针对现有由饱和盐酸水解制备氨基葡萄糖盐酸盐方法因反应条件剧烈容易造成产品炭化的问题 ,研究了相对温和的条件下壳聚糖的水解。结果表明 ,该条件下 ,非晶态壳聚糖非常有利于氨基葡萄糖盐酸盐生成 ,而粒径这一通常在研究固 -液非均相反应时所要考虑的因素 ,对壳聚糖水解并未产生明显影响。使用非结晶态壳聚糖 ,3mol/L盐酸 ,90°C,经 5 h水解 ,氨基葡萄糖盐酸盐的收率可达 48%。     

壳聚糖改性膜材料的研究(Ⅱ)壳聚糖与甲基丙烯酸接枝共聚

以硝酸铈铵为引发剂引发壳聚糖（Cs)与甲基丙烯酸（MAA）接枝共聚。用元素分析，红外光谱。X-射线粉末衍射对接枝共聚物进行分析，并研究了接枝共聚物膜材料的力学性能和溶解性能。结果表明，由于接枝聚合，使Cs大分子原来的结晶结构受到破坏，韧性得到了一定的改善，经2%的氢氧化钠溶液处理过的Cs-g-MAA接枝共聚物膜，具有很好的耐溶剂性能。     

壳聚糖接枝聚乳酸共聚物性能及其体外释药行为研究

采用原位聚合法合成了含聚乳酸链段的壳聚糖接枝共聚物.通过X射线衍射(XRD)和热重(TG)分析研究共聚物的结晶性能和热失重行为.结果表明,共聚物的结晶度和热分解温度降低,壳聚糖的高结晶性能得到改善.接触角测试表明,相对于聚乳酸,共聚物材料具有较好的亲水性.通过溶剂挥发法制备了5-氟尿嘧啶/共聚物载药微球,并用紫外分光光...     

原位聚合尼龙6/纳米SiO2复合材料的研究

将经湿法处理的纳米SiO_2处理液直接加入到己内酰胺反应物中,原位水解开环聚合制备了尼龙6/纳米SiO_2复合材料,表征了该纳米SiO_2复合材料的相对分子质量、结晶结构和热性能等。结果表明,尼龙6纳米SiO_2复合材料随着纳米SiO_2含量的增加,尼龙6的相对分子质量降低,结晶度与熔点略有下降,储能模昔幅度提高。     

Radiation stability of PTFE with different crystallinity

In this work, the effects of radiation on polytetrafluoroethylene (PTFE) samples with different crystallinity were studied. Using Suwa's equation for calculating the number-average molecular weight of PTFE, the radiation-induced reduction in molecular weight was followed and the G values of scission of PTFE were also obtained on the basis of the changes in molecular weight. The G (scission) for as-polymerized PTFE was 2.15 ± 0.01, whereas for sintered sample, which has a relative low crystallinity, G (scission) = 6.0 ± 0.14. © 1993 John Wiley & Sons, Inc.     

高硅铝比NaY分子筛的合成

采用动态水热晶化法,利用工业原料不加模板剂直接合成高硅铝比的NaY分子筛,制备的NaY分子筛的硅铝物质的量比稳定在5.85~6.05,相对结晶度大于85%。考察了导向剂陈化时间及温度、体系碱度、预晶化温度及时间等对合成的NaY分子筛硅铝比和结晶度的影响,提出制备高硅NaY的最佳合成条件。     

Solid‐state polymerization and bulk crystallization behavior of poly(ethylene terephthalate) (PET)

The main variables involved in solid‐state polymerization of PET homopolymers, originally with molecular weight within the commercial range, were sequentially studied to determine their influence in polymerized products. These variables were precursor crystallinity, catalyst, and time and reaction temperature. An increasing molecular weight sequence was then used to study the bulk crystallization behavior with Avrami analyses. It was determined that thermal conditions at dissolution affect the prereaction morphology. This was important in the polymerization process because it was found that high crystallinity levels in precursors result in higher molecular weights. In agreement with other reports, typical catalysts used in melt polymerizations enhance postpolycondensation processes in the solid state. High reaction times and temperatures were also required to obtain high molecular weights. As the molecular weight increased, there was a decrease in nucleation density and Avrami analyses, applied to the isothermal bulk crystallization, indicating that the nucleation process changed from instantaneous to spontaneous with the increase in molecular weight. The consequences and relative importance of the observed results is discussed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 78–86, 2000     

含携带剂超临界CO_2诱导聚碳酸酯结晶的研究

利用含甲醇携带剂的超临界CO2(ScCO2)对由双酚A(BPA)和碳酸二苯酯(DPC)合成的聚碳酸酯(PC)预聚物进行了诱导结晶,所得结晶预聚物经固相缩聚得到了高分子量PC。采用凝胶渗透色谱(GPC)测定了产物分子量,并通过差示扫描量热仪(DSC)和X射线衍射仪(XRD)对产物进行了测试表征;考察了压力、温度和诱导时间等因素对PC结晶度的影响,以及不同结晶度的预聚物对缩聚产物分子量的影响。结果表明:随着温度的升高,PC结晶度先升后降,理想结晶温度为90℃;另外,结晶度随着压力的增大而增大,较佳的结晶压力为30 MPa;此外,在较高温度下PC预聚物的诱导结晶速度加快,并且相同条件下预聚物结晶度越大缩聚产物的分子量越大。     

Thermo-mechanical behaviour of Polyamide 6 chain extended with 1,1′-Carbonyl-Bis-Caprolactam and 1,3-Phenylene-Bis-2-Oxazoline

A commercial Polyamide 6 (PA6) was melt compounded by using a twin screw extruder with a combination of 1,1′-Carbonyl-Bis-Caprolactam (CBC) and 1,3-Phenylene-Bis-2-Oxazoline (PBO), in order to evaluate their effect on the chain extension behaviour of the resulting materials. An increase of the viscosity values with the chain-extender amount was evidenced by rheological tests on the compounded pellets and relative viscosity measurements on solubilized samples, while the opposite trend was determined increasing the residence time at elevated temperatures. The increase of the molecular weight due to the presence of CBC and PBO was confirmed by the reduction of carboxylic and aminic functionalities evidenced in end group analysis. DSC tests showed a reduction of the melting temperature and of the crystallinity degree proportionally to the chain extender amount. Elastic modulus of the chain-extended materials was similar to that of the corresponding PA6 grades at different molecular weight, while crystallinity drop due to chain extension determined an increase of the strain at break values.     

低相对分子质量反式聚丁二烯的合成及表征

采用负载钛催化体系溶液淤浆聚合法,以氢气为相对分子质量调节剂,合成了低相对分子质量的反式—1,4—聚丁二烯(LMTPB),通过IR,DSC表征了其结构及结晶状态。结果表明,随着氢气压力升高,LMTPB的相对分子质量降低;当氢气分压超过3MPa时,聚合物的特性黏数降至0.5dL／g,相对分子质量在2000以下。随氢气压力提高,反式—1,4—结构摩尔分数下降,但仍保持在86％以上,结晶度和熔点降低,溶解性提高。LMTPB是由相对分子质量大小和微观结构不同,结晶类型、结晶度和熔点不同的级分组成的混合物。     

多元环氧扩链剂（ADR）对PBAT的扩链改性及其耐老化性能的影响

将多元环氧扩链剂（ADR）在双螺杆中对聚对苯二甲酸?己二酸丁二酯（PBAT）进行挤出扩链反应改性,研究了添加不同含量ADR对PBAT端羧基含量、相对分子质量、力学性能、结晶度及色度的影响,并采用氙灯老化实验研究了老化时间对添加不同含量ADR的PBAT力学性能与相对分子质量的影响。结果表明,经ADR扩链后,PBAT的端羧基含量下降,力学性能和相对分子质量提高;当ADR添加量为1 %时,PBAT的端羧基含量下降尤为显著,从23.3 mol/t下降至13.8 mol/t,相对分子质量、结晶温度和力学性能有所提高;当ADR添加量为1 %时,样品的力学性能最优,在老化期间断裂伸长率高于其他样品,并且化学结构和相对分子质量体现出的耐老化性能较优,老化期间的相对分子质量始终高于其他样品。     

1,2-丙二醇对可生物降解聚丁二酸丁二醇酯的共聚改性

以丁二酸、丁二醇和1,2-丙二醇为原料,采用溶液结合熔融缩聚合成法,得到了一系列聚(丁二酸丁二醇酯-co-丁二酸1,2-丙二醇酯)共聚物P(BS-co-PS)。利用1HNMR、GPC和X射线衍射等方法对共聚物的组成、分子量及其分子量分布、热学性能、结晶性能、力学性能等进行了研究。结果表明:反应4h,即可得到数均分子量60000以上的聚(丁二酸丁二醇酯-co-丁二酸1,2-丙二醇酯)共聚物P(BS-co-PS),分子量分布均小于2.0;随着1,2-丙二醇添加量的增加,共聚物的结晶度降低,熔点下降,但断裂伸长率明显增加,当添加量为30%(摩尔分数)时,断裂伸长率达到417%,表明共聚物具有良好的延展性能;所有共聚物的热分解温度均在300℃以上,具有良好的热稳定性。     

Degradation of PLA fibers at elevated temperature and humidity

The hydrolytic degradation of poly(lactic acid) (PLA) devices has previously been reported as size dependent for devices such as plates, microspheres, and films between 2 and 0.3 mm in thickness or diameter. In this study, the effect of fiber diameter on the degradation characteristics of PLA fiber of two diameters, 32 µm (PLA32) and 118 µm (PLA118), aged at 40, 60, and 80°C with 100% relative humidity, was investigated. Additionally, both PLA32 and PLA118 were aged at 40 and 60°C under nitrogen purge. The degradation of the fibers was evaluated based on changes in the total weight, crystallinity, and molecular weight of the samples. Both diameters exhibited similar total weight loss, crystallinity, and molecular weight loss profiles under each set of degradation conditions. Two models for the change in molecular weight were compared: a first order model and an autocatalytic model. For the obtained data, both models provided a reasonable fit of the molecular weight data. Based on the rate constants obtained for each model, the activation energy for PLA degradation was calculated (26.3 kcal mol^?1 for the first order model and 22.4 kcal mol^?1 for the autocatalytic model). The activation energies obtained were close to other values reported in the literature for PLA hydrolysis. POLYM. ENG. SCI., 55:1652–1660, 2015. © 2014 Society of Plastics Engineers